The miniaturization of semiconductor devices and the like is advantageous in bringing about an improvement in performance and function (higher-speed operation, lower power consumption, etc.) and a reduction in cost and thus has been accelerated more and more. The lithography technique has been supporting this miniaturization and transfer masks are a key technique along with exposure apparatuses and resist materials.
In recent years, the development of the half-pitch (hp) 45 nm to 32 nm generations according to the semiconductor device design rule has been progressing. This corresponds to ¼ to ⅙ of a wavelength 193 nm of ArF excimer laser exposure light (hereinafter referred to as “ArF exposure light”). Particularly, in the hp45 nm and subsequent generations, only the application of the resolution enhancement technology (RET) such as the conventional phase shift method, oblique illumination method, and pupil filter method and the optical proximity correction (OPC) technique has been becoming insufficient, and the hyper-NA technique (immersion lithography) and the double exposure (double patterning) technique have been becoming necessary.
In the meantime, circuit patterns necessary in the semiconductor manufacture are exposed in sequence onto a semiconductor wafer by a plurality of photomask (reticle) patterns. For example, a reduced projection exposure apparatus with a predetermined reticle set therein repeatedly projects and exposes patterns while sequentially shifting projection regions on a semiconductor wafer (step-and-repeat system), or repeatedly projects and exposes patterns while synchronously scanning the reticle and a semiconductor wafer with respect to a projection optical system (step-and-scan system). By this, a predetermined number of integrated circuit chip regions are formed in the semiconductor wafer.
A photomask (reticle) has a region formed with a transfer pattern and a peripheral region thereof, i.e. an edge region along four sides in the photomask (reticle). When exposing the transfer pattern of the photomask (reticle) while sequentially shifting projection regions on a semiconductor wafer, the transfer pattern is exposed and transferred onto the projection regions so that the photomask peripheral regions overlap each other for the purpose of increasing the number of integrated circuit chips to be formed. In order to prevent exposure of a resist on the wafer due to such overlapping exposure, a light-shielding band (light-shielder band or light-shielder ring) is formed in the peripheral region of the photomask by mask processing.
The phase shift method is a technique of giving a predetermined phase difference to exposure light transmitted through a phase shift part, thereby improving the resolution of a transfer pattern using interference of light.
As photomasks improved in resolution by the phase shift method, there are a substrate dug-down type in which a shifter part is provided by digging down a quartz substrate by etching or the like, and a type in which a shifter part is provided by patterning a phase shift film formed on a substrate.